title: Blood pressure levels and brain volume reduction: a systematic review and meta-analysis.
abstract: OBJECTIVE
  High blood pressure (BP) levels may be associated with brain volume reduction and may contribute to brain atrophy in key brain regions involved in cognition and susceptible to neurodegeneration in Alzheimer's disease. The purpose of this work was to systematically review and quantitatively synthesize the association of BP levels with brain volume reduction in humans.
  
  
  METHODS
  An English Medline, Cochrane Library and PsycINFO search was conducted in June 2012 using the Medical Subject Heading terms 'Blood pressure', 'Hypertension', 'Brain mapping' and 'Brain atrophy'.
  
  
  RESULTS
  Of the 609 screened abstracts, 28 studies (4.6%) were included in the qualitative analysis. Twenty-six studies (92.9%) showed a significant association of higher BP levels and/or hypertension with total and/or regional brain volume reduction, the frontal and temporal lobes being particularly affected. In addition, four other studies reported an association between lower BP levels and brain volume reduction. Due to the heterogeneity of methodology and outcomes, random-effects meta-analyses of the mean difference of brain volume could be performed on only seven studies, with a total of 709 cases with hypertension and 1001 controls without hypertension. The findings showed no between-group difference regarding the whole-gray matter volume (summary mean difference = 2.42 cm [95% confidence interval (CI): -2.13 to 6.96]). Conversely, cases with hypertension exhibited lower hippocampus volume compared with controls [summary mean difference = -0.10 cm (95% CI: -0.17 to -0.02)].
  
  
  CONCLUSIONS
  These findings provide evidence that high BP levels lead to brain volume reduction, specifically in hippocampus, and may be an important factor that contributes to neurodegeneration in Alzheimer's disease.
authors.affiliation: Division of Geriatric Medicine, Department of Neuroscience, Angers University Hospital, 49933 Angers Cedex 9, France. OlBeauchet@chu-angers.fr
authors.forename: Olivier
authors.initials: O
authors.lastname: Beauchet
authors.forename: Sébastien
authors.initials: S
authors.lastname: Celle
authors.forename: Frédéric
authors.initials: F
authors.lastname: Roche
authors.forename: Robert
authors.initials: R
authors.lastname: Bartha
authors.forename: Manuel
authors.initials: M
authors.lastname: Montero-Odasso
authors.forename: Gilles
authors.initials: G
authors.lastname: Allali
authors.forename: Cédric
authors.initials: C
authors.lastname: Annweiler
mesh_terms: D000544:Alzheimer Disease / Q000503:physiopathology; D001284:Atrophy; D001794:Blood Pressure; D001921:Brain / Q000033:anatomy & histology / Q000503:physiopathology*; D001931:Brain Mapping / Q000379:methods; D006624:Hippocampus / Q000033:anatomy & histology / Q000503:physiopathology; D006801:Humans; D006973:Hypertension / Q000150:complications / Q000503:physiopathology; D019636:Neurodegenerative Diseases / Q000503:physiopathology; D009929:Organ Size; D012107:Research Design; D013997:Time Factors